1. Field of the Invention
The following specification describes a unique mechanism for permitting fine adjustment of the height of a biasing wheel of a biasing guide of the general type found in Schwoch, et al. U.S. Pat. No. 3,738,403. Such devices are intended to assist in stabilization of a work piece in a machine tool to prevent kickback and other problems related to the operation. Such devices also assist in holding down larger work pieces and materially assist the operator in handling the work piece during operation.
The present invention deals with one aspect of the biasing guide, which has, over the years, proven to be particularly troublesome.
In Schwoch, et al. an initial height adjustment for the biasing roll did not exist. No matter how thick the work piece, the roll would simply be lifted to that height, and the pressure against the work piece would be a function of the spring rate used to provide the downward bias on the shaft. As a consequence, the thicker the work piece, the greater the pressure against it at the point where it was engaged by the biasing roll. As a result, the operator would find that thicker work pieces were far more difficult to manipulate and maneuver, thereby greatly diminishing the value of the bias guide.
2. Overview of Prior Art
Since the issuance of Schwoch, et al. in 1973, there have been several major improvements, and the device has been developed to a high degree of sophistication, and whereas the objectives of the device remain basically the same as those espoused for Schwoch, et al., as a result of many refinements, the most successful present day biasing guide, sold internationally under the trademark "SHOP HELPER", has enjoyed a high degree of acceptability among commercial users, as well as in the home workshop.
Schwoch, et al. was a pioneer in such devices. That patent describes and claims a device which biases or urges a work piece on a radial saw or the like, towards a fence where it holds the piece in place during the sawing operation. The Schwoch apparatus involves the pivoting of a shaft having a biasing wheel at the other end. A spring biases the shaft, and thus the wheel, downward towards the deck or working surface of a machine tool, such as a radial saw. Schwoch suggested, as an alternative to the pivoting shaft, a resilient arcuate shaft having the biasing wheel at one end, and, again, employing a spring to urge the wheel against the working surface of the machine tool.
As the rather primitive Schwoch structure began to evolve, it was found useful to segregate the height and bias pressure functions of the device so that each might be individually controlled. In this manner, one could adjust the height of the bias roll to accommodate various work piece sizes, and then adjust the tension on the roll to achieve the control function while maintaining ease of operation. Several attempts were made at finding ways to adjust the height of the roll initially without unduly complicating the structure, or making it inordinately expensive to manufacture. One such effort involved the drilling of several holes in the side walls along the leading edge, and by use of a pin extending between the walls, the height was pre-adjusted. Such a configuration was limited, however by the spacing of the holes. Other efforts were equally deficient.